National Semi sued a Taiwanese chip maker.

The suit, filed in Santa Clara County Superior Court, seeks to block United Microelectronics Corp. and its local U.S. representative, NMC Technology Inc., from selling in the United States an integrated circuit that National Semiconductor claims is based on its own design. The chip involved in the lawsuit is a universal asychronous receiver transmitter, which has an estimated world market of $25 million to $30 million a year.